Gambas/Graphics

Back to Gambas

If you want to produce some graphics in gambas you should get used to the drawingarea control.

Draw a Line

This little program will draw a line. You have to start a new graphics project. You take a form as your start form. You need a drawingarea and a commandbutton on the form to get it going.

 PUBLIC SUB Button1_Click()
 Draw.Begin(DrawingArea1)
 Draw.Line(1, 130, 500, 400)
 Draw.End
 END

When you want to draw some more lines, then try this example:

 PUBLIC SUB Form_Open()
 DIM B AS Integer 
 Draw.Begin(DrawingArea1)
 FOR B = 1 TO 200 STEP 10 
  Draw.Line(1, B, 500, B)
 NEXT 
 Draw.End
 END

Some other lines are drawn here:

 PUBLIC SUB Button1_Click()
 DIM B AS Integer 
 Draw.Begin(DrawingArea1)
 ' Draws a line horizontally across the centre of the form
 Draw.Line (0, ME.Height / 2, ME.Width, ME.Height / 2)
 ' Draws a line vertically down the centre of the form
 Draw.Line (ME.Width / 2, 0,ME.Width / 2, ME.Height)
 ' Draws a line from the top left, to the bottom right
 Draw.Line (0, 0,ME.Width, ME.Height)
 ' Draws a line from the top right, to the bottom left
 Draw.Line (ME.Width, 0,0, ME.Height)
 Draw.End
 END

When you want to manipulate the width of your line , then try this example:

 PUBLIC SUB Form_Open()
 DIM B AS Integer 
 Draw.Begin(DrawingArea1)
 Draw.Line(10,100, 20, 100)
      FOR B = 1 TO 100 STEP 10 
       Draw.LineWidth=B 
       Draw.Line(10+B,100, 20+B, 100)
      NEXT 
 Draw.End
 END

If you want to change the color of your line to white, then try this example:

 Draw.Begin(DrawingArea1)
 Draw.ForeColor = &HFFFFFF
 Draw.Line(1, 130, 500, 400)
 Draw.End

The next small example will draw a box and fill it with white color.

 PUBLIC SUB Button1_Click()
 Draw.Begin(DrawingArea1)
  Draw.FillColor = &HFFFFFF
  draw.FillStyle = 1
  'draw.ForeColor = &HFFFFFF the outline will be white also
  Draw.Rect (100, 100,200,200)
 Draw.End
 END

The Spiral Program

This program shows you a nice spiral. There is no scale command in Gambas (at least, not yet). Therefore the x and y coordinates are transformed in the program. The coordinate system ranges from xmin = - 2 to xmax = 2 and ymin = - 2 to ymax = 2.

You need a Drawingarea and a Commandbutton to get the example going.

How does this look ? See [1]

The code:

 PUBLIC SUB Button1_Click()
 DIM dymax AS Integer
 DIM dymin AS Integer 
 DIM ymax AS Integer
 DIM ymin AS Integer
 DIM y AS Float
 DIM dy AS Float
 DIM dyi AS Integer
 DIM dxmax AS Integer
 DIM dxmin AS Integer 
 DIM xmax AS Integer
 DIM xmin AS Integer
 DIM x AS Float
 DIM dx AS Float
 DIM dxi AS Integer
 DIM k AS Float 
 DIM a AS Float 
 DIM w AS Float
 dymax = DrawingArea1.Height
 dymin = 0 
 ymax = 2
 ymin = -2
 dxmax = DrawingArea1.Width
 dxmin = 0 
 xmax = 2
 xmin = -2 
 'x-axis is drawn 
 FOR x = xmin TO xmax STEP 0.005
 y = 0 
 dy = CFloat(y - ymin) / (ymax - ymin ) * (dymax - dymin) + dymin 
 dx = CFloat(x - xmin) / (xmax - xmin ) * (dxmax - dxmin) + dxmin 
 dyi = Fix(dy)
 dxi = Fix(dx) 
 Draw.Begin(DrawingArea1)
 Draw.Point(dxi,DrawingArea1.Height- dyi)
 Draw.End
 NEXT 
 'y - Axis is drawn
 FOR y = ymin TO ymax STEP 0.005
 x = 0 
 dy = CFloat(y - ymin) / (ymax - ymin ) * (dymax - dymin) + dymin 
 dx = CFloat(x - xmin) / (xmax - xmin ) * (dxmax - dxmin) + dxmin 
 dyi = Fix(dy)
 dxi = Fix(dx) 
 Draw.Begin(DrawingArea1)
 Draw.Point(dxi,DrawingArea1.Height- dyi)
 Draw.End
 NEXT 
 'Here the spiral starts
 FOR k = -100 TO 150 STEP 0.5
 a = 0.97
 'Distance from 0,0 to the point 
 w = 0.15
 'Angle under whiche the point is seen from the origin
 a = a ^k 
 w = w * k 
 x = a * Cos(w)
 'x coordinate of each point
 y = a * Sin(w)
 'y coordinate of each point
 dy = CFloat(y - ymin) / (ymax - ymin ) * (dymax - dymin) + dymin 
 dx = CFloat(x - xmin) / (xmax - xmin ) * (dxmax - dxmin) + dxmin 
 dyi = Fix(dy)
 dxi = Fix(dx) 
 Draw.Begin(DrawingArea1)
 Draw.Point(dxi,DrawingArea1.Height- dyi)
 Draw.End
 NEXT
 END